The invention generally relates to single chip devices and, more particularly, the invention relates to single unit position sensors.
Global Positioning Systems are widely used as navigational aids. Among other things, they typically include a high performance RF receiver to receive RF signals from orbiting satellites, and a microprocessor to calculate position information based on the received RF signals. Because they must receive the RF signals to calculate position, Global Positioning Systems rely upon an unobstructed line of sight to the satellites.
There are instances, however, when the line of sight to the satellites is obstructed. For example, tall buildings in urban areas can obstruct the line of sight to the satellites. The art has responded to this problem by coupling Inertial Motion System chips with Global Positioning System chips. For example, an IMEMS(copyright) gyroscope, available from Analog Devices, Inc. of Norwood, Mass., could be used in this application. Accordingly, when the receiver loses contact with the satellites, the Inertial Motion System can deliver movement information to the processor, which then can calculate the actual position information.
There are a number of disadvantages associated with using a two-chip design. Specifically, as known by those skilled in the art, using two chips to accomplish the overall functionality typically increases the size, power requirements, and cost of the device, while also reducing reliability. The currently available manufacturing processes for forming currently available Global Position Sensors and Inertial Motion Sensors, however, are incompatible and thus, cannot produce the combined functionality on a single chip.
In accordance with one aspect of the invention, a position sensor includes a receiver capable of receiving a position signal from an external source, and an inertial motion unit capable of sensing movement and producing a movement signal based upon the sensed movement. The position sensor also includes a processor operatively coupled with the receiver and the inertial motion unit. The processor is capable of calculating position information based on at least one of the position signal and the movement signal. Moreover, the receiver, inertial motion unit and processor are formed on a single chip.
In illustrative embodiments, the single chip is a MEMS device. The receiver also may include radio frequency circuitry, while the inertial motion unit may include at least one of an angular rate sensor and an accelerometer. The processor may include a microprocessor. In some embodiments, the receiver is formed at least in part from a material having a higher electron mobility than that of single crystal silicon. In addition, the inertial motion unit may include first structure capable of moving relative to second structure, where the first structure is formed by a material comprising geranium. For example, the first structure may be a beam that moves relative to a stationary portion of the remainder of the inertial motion unit. Interdigitated fingers, for example, may sense the movement.
In accordance with another aspect of the invention, a single unit MEMS device (i.e., formed on a single chip or die) has a movable structure capable of moving relative to other portions of the MEMS device, and high performance circuitry capable of processing a position signal received from an external source. The position information is calculable based upon at least one of the movement of the movable structure and the processed position signal from the circuitry.
The circuitry illustratively includes a set of transistors capable of processing a signal having a frequency that is substantially equal to or greater than about 200 megahertz. For example, the circuitry may include radio frequency circuitry for processing the position signal. In addition, the circuitry may be formed at least in part from a material having a higher electron mobility than that of single crystal silicon.
In some embodiments, the movable structure is a part of at least one of a gyroscope and an accelerometer. The MEMS device thus may have processor circuitry operatively coupled with radio frequency circuitry, where the processor circuitry is capable of determining position based on at least one of the movement of the movable structure and the processed position signal from the radio frequency circuitry. The movable structure illustratively is formed from a material formed at least in part from geranium.
In accordance with other aspects of the invention, a MEMS device has a movable structure capable of moving relative to other portions of the MEMS device, and circuitry capable of processing a signal having a frequency that is substantially equal to or greater than about 200 megahertz. The movable structure and circuitry cooperate to deliver an output signal. Such output signal can include position information.
In some embodiments of the invention, the movable structure is a part of at least one of an angular rate sensor and an accelerometer. The circuitry also may be capable of processing a signal having a frequency that is substantially equal to or greater than about 1.5 gigahertz.
In accordance with still other aspects of the invention, a multi-layered wafer for producing a MEMS device includes first and second layers, and an oxide layer between the first and second layers. The wafer further includes a material layer formed on one of the first and second layers, where the material layer is formed (at least in part) from a material having a higher electron mobility than that of either of the first and second layers.
In accordance with yet another aspect of the invention, a method of producing a MEMS device provides a composite wafer having a silicon on insulator wafer having first and second silicon layers, and an oxide layer between the silicon layers. The composite wafer also includes a material layer on the silicon on insulator wafer, where the material layer includes a material having a higher electron mobility than that of any material on the silicon on insulator wafer. The method then forms electronics (i.e., circuitry) on the material layer.
Structure may be formed on one of the first and second silicon layers. The electronics may include RF circuitry.
In accordance with another aspect of the invention, a method of forming a MEMS device provides a wafer having a material layer deposited on a first silicon layer. The material layer includes a material having a higher electron mobility than that of the silicon layer. The method forms circuitry on the material layer, and forms a second layer, where the material layer is between the first silicon layer and the second layer. The method then forms structure on the second layer.